If you are after a paintball marker that looks like a MP5, you'll be a lot better off buying this than upgrading a Tippmann. The SIM-5 not only incorporated the overall look of the MP5, it has all the details as well, which Tippmanns cannot acheive without extreme modification. The two main things you cannot get on a Tippmann is the position and details of the cocking handle, and the trigger assembly (realistic safety).

----Performance----

This marker is accurate, but it might be a bit loud for some poeple. The '5 does not need a aftermarket barrel like most low end markers does, but it is also very hard to find an aftermarket barrel for it. The barrel itself does not have any ports on it, which results in the marker being quite loud. The quick release barrel is a nice feature as well. It lets you pull out the barrel just by pulling out a pin, which lets you clean the barrel on the field really quickly.

----MAINTANENCE----

The SIM-5 does require more maintanence than Tippmanns, but it would be well worth it. The maintanence is very easy though. All you need to do is pretty much keep the internals lubed.

----CUSTOMIZABILITY----

The marker is significantly less customizalbe than Tippmanns, but it doesn't need as much either. You do not need any upgrades to make the marker milsim. There is also no need for a aftermarket barrel. You can choose to purchase the sight rail and mount a sight on it. There are also 3 weaver rails on the stock RIS handguard. You can mount lasers, tactical lights, foregrips, Q Loaders etc on the rails.

----DURABILITY----

I do not have much problems with the durability of this marker, dispite many people saying the plastic parts break easily. The only problem I see it the trigger assembly, where it is screwed onto the upper reviever, it might crack if you screw it too tight. I do not see much need to disassemble the trigger assembly though.

Conclusion:

I would recommend the SIM-5 to anyone looking for a milsim paintball marker, or even people who just want a reliable, easy-to-maintain, woodsball or rec ball marker.